The present invention is directed to a device for setting anchors formed of an expansion sleeve and an anchor rod with an expanding member on the end of the anchor rod. A housing abuts in the axial direction against a trailing end of the expansion sleeve. A socket is in threaded engagement with the anchor rod and is rotatably supported relative to the housing. The socket has engagement means for rotating it about the axis of the anchor rod.
In the crack-prone tension zone of a structure, so-called undercut anchors are used for reasons of safety. Such undercut anchors are distinguished by a positive locking connection with the structure, so that the full anchoring value is maintained even if the borehole widens due to the development of cracks.
An anchor satisfying the above requirements is disclosed in EU-A-O 226,525. To attain the full anchoring value with this anchor a prestress is required. Due to the prestress, which is achieved by a suitable device, segments of the expansion sleeve are displaced into the undercut region of a borehole.
The device for prestressing undercut anchors as disclosed in EU-A-O 226,525 has the particular disadvantage that the thread on the anchor rod must be used as the prestressing means. As a result, this thread is subject to a large load during the prestressing or pretensioning operation, and in some circumstances can lead to damage. Furthermore, because of the usual pitch of such a thread extraordinarily high torque must be provided for the pretensioning operation.